KR20150118169A - Sealing apparatus for a fuel cell stack - Google Patents

Abstract

Wherein the fuel cell stacking assembly includes a fuel cell stack, each fuel cell having an air flow conduit having a supply / discharge vent hole disposed in the air flow side of the stack, An array is formed over the ventilation surface. The membrane is movable between a first configuration in which the ventilating surface is obscured and a second configuration in which the ventilating surface is not covered. The membrane is retractable between the first configuration and the second configuration. Thus, the aeration of the fuel cell stack is controlled by the position of the membrane during, for example, fuel cell start-up and / or shutdown procedures or during hydration control of the fuel cell.

Description

[0001] SEALING APPARATUS FOR A FUEL CELL STACK [0002]

The present invention relates to an electrochemical fuel cell disposed in the form of a laminate, and more particularly to an air flow system for venting such a fuel cell stack.

Conventional electrochemical fuel cells generally convert fuel and oxidant, both in the form of a gas stream, into electrical energy and reaction products. A typical type of electrochemical fuel cell for reacting hydrogen and oxygen comprises a polymeric ion transport membrane, also known as a proton exchange membrane (PEM), in a membrane-electrode assembly (MEA) Lt; / RTI > Both (i.e., hydrogen ions) are balanced through electrons conducted through the membrane and conducted through the anode and cathode of the fuel cell. To increase the available voltage, a laminate is formed that includes a plurality of series connected MEAs arranged to have separate anode and cathode fluid flow passages. These stacks typically comprise a plurality of individual fuel cell plates held together by end plates at either end of the stack.

Because the reaction of the fuel and the oxidant produces heat as well as power, the fuel cell stack requires cooling to prevent damage to the fuel cell once the operating temperature is reached. Cooling may be achieved by forcing air through the fuel cell stack. For an open cathode stack, the oxidant flow path and the coolant flow path are identical, i.e., forcing air through the cathode fluid flow path is to supply the oxidant to the cathode and cool the stack. In applications of lower power, or in periods of low demand, cooling and oxidant supply may be alternatively provided by diffusing air into the oxidant / coolant flow path, i.e., without forced venting. In other fuel cell stacks, the oxidant air may be provided separately from the cooling mechanism, which may be provided, for example, by a cooling water circuit.

The present invention is applicable to this fuel cell stack type.

It may be useful to prevent or limit air flow through the cathode fluid flow passages during start-up or shutdown of the fuel cell stack, or during periods of very cool ambient conditions. Various methods have been proposed in the prior art for controlling air flow through a cathode fluid flow passage using a valve or shutter. It is an object of the present invention to provide a simple and efficient alternative approach.

Membranes, catalytic materials, and diffuser media found in fuel cells can be easily contaminated from the outer source (question), which can degrade the performance of the fuel cell stack over time. It is desirable to limit the exposure of the sensitive portion of the fuel cell to gases, other airborne contaminants and particles that can degrade the catalyst. In particular, when transporting fuel cell stacks and when the fuel cell stack environment is not controlled (for example, when there is a risk of contamination from a transient or temporary air pollution source) During the period, it is desirable to close the air flow path to the cathode fluid flow path. It is an object of the present invention to provide a simple and efficient method of limiting exposure to contamination of sensitive parts of a fuel pneumatic stack.

According to one aspect, the present invention provides a fuel cell stack assembly,

A fuel cell stack, wherein each fuel cell has an air flow conduit having a supply / discharge vent hole disposed on the vent face of the stack, the vent hole having an array over the vent face of the stack Said fuel cell stack being formed of a fuel cell stack;

And a membrane that is movable between a first configuration in which the vent surface is obscured and a second configuration in which the vent surface is not obscured.

The membrane may be retractable between the first configuration and the second configuration. The membrane may include a first portion providing at least one aperture configured to expose the aeration surface when disposed on the aeration surface and a second portion configured to cover the aeration surface when disposed on the aeration surface have. The fuel cell stack assembly may further include a first receptacle for receiving the first portion of the membrane in a rolled state when the membrane is in the first configuration. The fuel cell stack assembly may further include a second receptacle for receiving the second portion of the membrane in a rolled state when the membrane is in the second configuration. The first receptacle may be disposed at an outer edge of the ventilation surface. The first and second receptacles may be disposed at opposite outer edges of the ventilating surface. The fuel cell stack assembly may further include a motor configured to drive the membrane between the first configuration and the second configuration. The fuel cell stack assembly may further comprise an outer seal disposed along the periphery of the venting surface, the membrane being positioned to contact at least the outer seal in the first configuration. The membrane may be positioned to be in sliding contact with at least a portion of the outer seal during movement to the first configuration. The controller may be configured to operate the membrane between the first configuration and the second configuration as part of a fuel cell startup and / or shutdown procedure. The membrane may be movable to an intermediate configuration in which some air flow conduits of each of the cells of the fuel cell stack are obscured and other air flow conduits of each of the cells of the fuel cell stack are not obscured. The membrane may be movable in a configuration wherein the air flow conduit of the first selected cell in the fuel cell stack is obscured and the air flow conduit of the second selected cell in the fuel cell stack is unobstructed. The controller may be configured to operate the membrane between the membrane configurations according to the hydration level of the fuel cell.

According to another aspect, the present invention provides a method of operating a fuel cell stack assembly,

Mounting a movable membrane on a fuel cell stack, wherein each fuel cell has an air flow conduit having a supply / vent vent located on the vent face of the stack, Mounting the movable membrane to form an array over the ventilating surface;

And driving the membrane between a first configuration in which the vent surface is obscured and a second configuration in which the vent surface is not obscured.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:
1 shows a perspective view of a fuel cell stack in a state in which a ventilation surface is covered by a membrane;
2 shows a perspective view of a fuel cell stack in a state in which a ventilation surface is not covered by a membrane;
3 shows a front view of a ventilating frame having an elastomeric outer seal;
Figure 4 shows a partial perspective view of the ventilation frame of Figure 3 with a membrane receptacle disposed at one edge;
Figure 5 shows a perspective view of an enlarged portion of the membrane receptacle of Figure 4;
Figure 6 shows a perspective view of the unwound membrane for use in the system of Figures 1-5.

Throughout this specification, the terms "upper," "lower," "horizontal," "vertical," "left," "right," "upper," "lower," " And adverbial derivatives are used in the context of orientations of the fuel cell stacks provided in Figures 1 and 2. However, such descriptors may not be construed as limiting the intended use or orientation of the claimed and claimed invention It is not intended in such a way.

Figures 1 and 2 illustrate a fuel cell stack 1 comprising a stack of individual fuel cells 16, which has a visible venting surface 2 in Figure 2 on the front of the stack Collectively. For example, if the laminate is of a construction that requires forced venting through the laminate, a corresponding vent surface may be present on the opposite side of the laminate. The ventilating surface 2 generally comprises an array of vent holes in a plurality of fuel cells 16 which oxidant air is introduced into the cathode fluid flow passages of each cell 16 and / . This allows the oxidant to reach the membrane-electrode assembly of each cell 16, and / or allows humidified air to escape from the MEA. As shown in FIG. 2, each of the individual cells 16 occupies a horizontal plane, and the ventilating plane 2 corresponds to the edge of each of the cells 16. However, in alternative arrangements, each of the individual cells 16 may occupy a vertical plane.

A variety of fuel cell support systems 3 may be disposed on and around the face of the fuel cell stack.

A frame 4 is located on the ventilating face 2 which has one or more openings 5a, 5b and 5c and permits passage of air through the ventilating face 2. The frame 4 functions as a housing and guide for the flexible membrane 6 (visible in Fig. 1), which has a first configuration (Fig. 1) in which the aeration surface 2 is obscured and a second configuration The second configuration is not blocked.

Each of the pair of receptacles 7, 8 provides a chamber 13 (visible in Fig. 6) for receiving at least a portion of the soluble film 6. The chamber 13 of the first receptacle 7 may be configured to receive a blocking portion of the membrane 6 when the laminate venting surface 2 is not covered, The chamber 13 may be adapted to receive a non-occlusive portion of the membrane 6, for example, when the laminate venting surface 2 is obscured. In the preferred embodiment as shown, the receptacles 7, 8 are configured as cylindrical housings, although other shapes are possible.

3 shows a front view of the frame 4 which includes a first and a second receptacles 7 and 8, holes 5a, 5b and 5c and a frame on the front face of the fuel cell stack 1 And a fixing point 18 for a bolt or other mechanism for fixing. The frame 4 also includes an outer seal 9, which extends along the periphery of the frame to provide a fluid seal for the membrane 6. Additional seals (not shown) may be provided in the column 10 dividing the holes 5a, 5b, 5c. One example of an outer seal is an O-ring type seal partially disposed in a groove in the retention channel of the frame 4 surface, with a portion of the O-ring projecting from the surface of the frame. In addition, the frame 4 may include a plurality of holes 20 or cut-out slots 21 that allow air flow to the collector plate, which may typically be found above and below the fuel cell stack.

4 shows a schematic view of a part of the outer seal 9 which slightly protrudes from the front face 11 of the frame 4, the first receptacle 7, the holes 5a, 5b, 5c and the frame 4. Fig. It is also visible that the slot 12 extends over the width of the frame 4, approximately corresponding to the width of the holes 5a, 5b, 5c and the margin up to at least the margin seal 9 beyond this hole. The slot 12 allows the membrane 6 to be moved into and out of the receptacle 7 and keeps this film flat against the outer seal 9. Corresponding slots are also found at the upper edge of the frame 4, which enables the membrane 6 to move in and out of the other receptacle 8 in a similar manner.

5, a perspective view of the partially cut frame 4 shows the inner chamber 13 of the receptacle 7 receiving the membrane 6. As shown in Fig. The membrane 6 is moved into and out of the chamber 13 by the slot 12 which is sufficient to tension and hold the membrane in place when the membrane is driven through the slot 12, 15, which weakly hold the membrane 6 being moved through the slot, such that it is not sufficient to prevent the membrane from slipping between the slots.

Preferably, the slot seal 14,15 comprises a 100 micron thick Kapton sheet or a 50 micron thick stainless steel sheet, or any other low cost, and may be coated with a suitable lubricant. The outer seal 9 (and any other seal of the column 10) may also be coated with a suitable lubricant. Preferably, any lubricants or lubricity coatings used are free of materials that can contaminate the chemically sensitive components of the fuel cell, such as MEAs. Silicone-free lubricants may be desirable.

Fig. 6 shows a perspective view of the film 6 in its unturned state, suitable for use with the frame 4. Fig. The membrane 6 comprises a sheet material which can be used to cover the air-permeable surface by providing a barrier or partition wall across the holes 5a, 5b, 5c. 6, the membrane 6 is provided with holes 62a, 62b and 62c which correspond roughly in size and shape to the holes 5a, 5b and 5c of the frame 4 And has a first portion 61. The second portion 63 of the membrane 6 is non-breaking or continuous over at least as large an area as the area of the holes 5a, 5b and 5c of the frame 4 and, therefore, , 5b, 5c) can be completely covered or blocked.

The membrane is rollable, preferably in a compact roll, when received into the first and second remainder turbines 7, 8.

The membrane 6 also includes a plurality of distinct apertures 22 or cut slots 23 corresponding to the apertures 20 and cut slots 21 of the frame 4 described with respect to FIG. It is possible.

In normal use, one of the portions 61, 63 of the membrane is received in each receptacle 7 or 8 while the other portion 61, 63 is received in a frame (not shown) defining holes 5a, 5b, 5c 4). Thus, in a first configuration, which may be regarded as an ' vent opening ' configuration, the first portion 61 of the membrane 6 extends over the portion of the frame 4 defining the holes 5a, 5b, And the second portion 63 of the membrane 6 is wound in the upper receptacle 8. The first portion 61 of the membrane 6 is wound in the lower receptacle 7 and the second portion 63 of the membrane 6 Is laid over a portion of the frame defining the holes 5a, 5b, 5c to cover the hole.

Each of the receptacles 7 and 8 preferably includes a motor drive arrangement configured to pull the membrane into the chamber 13 and wind the membrane around the spindle of the chamber. The motor drive arrangement may be disposed in each chamber, or may be located at one or both axial ends of each receptacle. By providing a motor at each end of the membrane, i. E. To the receptacles 7 and 8, respectively, the membrane can be kept tensioned during movement by utilizing the pulling action of the appropriate motor drive. This pulling action may counter any friction applied by the movement of the membrane through the opposing slot seals 14, 15 adjacent the opposite receptacle.

An alternative method of retaining the tension of the membrane 6 during transfer may be used. For example, the motor at each end of the membrane may be configured to operate in opposition to the other motors to provide drive torque at one end of the membrane / frame and braking torque at the other end. Preferably, a brushless motor is used to minimize the risk of contamination of the air flow passage of the fuel cell stack. In other arrangements, a motor drive mechanism may be provided in one of the receptacles 7, 8, and a spring bias return mechanism may be provided in the other receptacle 7, 8. In this way, the motor drive mechanism provides a driving force for actuation of the membrane in one direction against the spring bias, and a spring bias provides the driving force for actuation of the membrane in the other direction.

The positioning of the film may be controlled in many different ways. For example, the membrane may have a series of longitudinally extending apertures (not shown) that may be read or counted by optical or mechanical or other sensors. Perforations of different shapes may be encoded for different positions. Alternatively, if a servo-controlled motor is used, positioning of the film may be accomplished by a suitable motor controller.

The frame 4 defines a shutter mechanism or closure mechanism for covering or partially covering the ventilating surface 2 of the fuel cell stack 1 together with the receptacles 7 and 8 and the membrane 6. [ do. The closure mechanism may be repeated on any other aeration surface of the fuel cell stack 1, such as on the opposite side to the front side visible in Figs. Each of the closure mechanisms may provide a cover for only a portion of the aeration surface 2 and a plurality of such closure mechanisms may be used to cover different portions of one aeration surface of the fuel cell stack.

When the shielding mechanism is provided on the opposite ventilation surface of the fuel cell stack, the shielding mechanism may be configured to operate in the opposite direction. One blocking mechanism may be configured to close the venting surface 2 by winding the membrane 6 in the upward direction while another blocking mechanism may be configured to close the downwardly facing venting surface. In this way, cutoff or reduction of air supply to all the cells 16 in the stack can be achieved in a short time.

Many different configurations of membranes can be used. The first portion 61 defines openings 5a, 5b, 5c (not shown) by defining holes 62a, 62b, 62c that are larger than the respective openings 5a, 5b, 5c of the frame 4, As shown in FIG. Alternatively, the first portion 61 may be configured to at least partially open the openings 5a, 5b, 5c, by defining a more restrictive aperture. The second portion 63 may be configured to completely cover the openings 5a, 5b, 5c or may provide several small holes that are limited in size or degree over the openings 5a, 5b, 5c have.

In another arrangement, the membrane 6 may comprise not only the first and second portions 61, 63 but also other portions. These other portions provide different degrees of occlusion between fully open and fully closed, such that the venting surface 2 or sides may be partially obscured. This may be useful, for example, when it is desirable to reduce the air flow to provide a reduction in transient and / or local air flow for the purpose of increasing the hydration level of any cell or any part of the cell . The membrane 6 may, for example, comprise a third portion and a fourth portion, wherein the third portion covers only a first subset of the total number of cells in the stack, Only the second subset of the total number of cells is covered. The first and second subsets may be mutually exclusive. In this way, the cells of the laminate may be selectively rehydrated into a group. The control mechanism may be provided to monitor the hydration level of the battery in the stack, and / or to monitor the battery voltage of the stack, and to control the positioning of the film to effect systematic rehydration.

It is possible that only a part of the ventilation holes of each battery 16 is covered in the above-mentioned other arrangement in which the membrane 6 moves in the direction parallel to the plane of the cell 16. [ In this way, for example, for a reduced power output, partial closure of each cell of the stack is possible simultaneously. In general, the membrane may be movable to an intermediate configuration in which some air flow conduits are obscured in each cell and other air flow conduits are not obscured.

Preferably, the apertures (e.g., 62a, 62b, 62c) of the membrane 6 are such that the leading and trailing edges of the membrane are moved through the slot 12 or through the seals 9, 14, , There is a rounded or inclined corner to reduce the risk of tearing.

The membrane 6 may be formed of any suitable flexible material. Preferably, the membrane may be wound into the chamber. Preferably, the membrane may be wrapped around one or more capstan in the receptacle, such as the receptacles 7, 8. The preferred material is capton which provides very low oxygen and CO2 permeation phases even in very thin sheet form. Another possible material for the membrane is a stainless steel sheet or film, or other metal sheet or film. Preferably, the membrane 6 used can provide a high degree of protection against the entry of compounds which may chemically damage sensitive parts of the fuel cell. Such compounds that are readily suspended in air include hydrogen sulfide.

The frame 4 is structured such that the membrane 6 is kept as close as possible to the air-permeable surface 2 of the fuel cell stack 1 so that a large number of individual cells constituting the air- There is a limited air circulation allowed between the vent holes. To achieve this, the membrane 6 may be in contact with, for example, a seal 9 on the inner side of the frame in the channel or groove of the frame, or on the back side closest to the laminate aeration surface. The edges of the membrane 6 may thus be configured to be movable in channels or grooves so that the front and back surfaces of the membrane are in sliding contact with the circumferential seal of the frame 4. [

The motor used to drive the membrane 6 may be an electric motor, an air motor or a hydraulic motor or any other suitable drive mechanism.

There are many and many advantages of the film occlusion mechanism as described herein. The film-clogging mechanism may require more time to wait for a spin-down of the fan, which may be forced to vent the stack, or to provide an active braking system for such a fan, Allowing very rapid interruption of air flow through the battery stack. Rapid interruption of air flow through the stack can prevent excessive dehydration of the battery during the shut-down process and force a rapid reduction of the current output through loss of the oxidant supply. Rapid shutdown without excessive water loss allows the fuel cell MEA to remain hydrated to provide faster and more efficient re-operation of the fuel cell stack. The system as described herein is expected to operate to close the ventilating surface of the fuel cell stack rapidly within 0.1 to 0.5 seconds with the appropriate motor drive apparatus and membrane type, depending on the size. However, it may be possible to achieve faster or slower times. The closure mechanism may also serve to provide air pulsating the laminate to further control laminate hydration.

Other embodiments are intended to be within the scope of the accompanying claims.

Claims (15)

In a fuel cell stack assembly,
A fuel cell stack, wherein each fuel cell has an air flow conduit having a supply / discharge vent hole disposed in the vent face of the stack, the vent hole forming an array over the vent face of the stack The fuel cell laminate;
And a membrane that is movable between a first configuration in which the aeration surface is obscured and a second configuration in which the aeration surface is not obscured.
The fuel cell stack assembly of claim 1, wherein the membrane is rollable between the first configuration and the second configuration.
The method of claim 1, wherein the membrane comprises a first portion providing at least one aperture configured to expose the aeration surface when disposed over the aeration surface, and a second portion configured to cover the aeration surface when disposed over the aeration surface, Fuel cell stack assembly.
3. The fuel cell stack assembly of claim 2, further comprising a first receptacle for receiving the first portion of the membrane in a rolled state when the membrane is in the first configuration.
5. The fuel cell stack assembly of claim 4, further comprising a second receptacle for receiving the second portion of the membrane in a rolled state when the membrane is in the second configuration.
5. The fuel cell stack assembly of claim 4, wherein the first receptacle is disposed at an outer edge of the ventilating surface.
6. The fuel cell stack assembly of claim 5, wherein the first receptacle and the second receptacle are disposed at opposite outer edges of the ventilating surface.
The fuel cell stack assembly of claim 1, further comprising a motor configured to drive a membrane between the first configuration and the second configuration.
2. The fuel cell stack assembly of claim 1, further comprising an outer seal disposed along a circumference of the ventilating surface, the membrane being positioned to contact at least the outer seal in the first configuration.
10. The fuel cell stack assembly of claim 9, wherein the membrane is positioned to be in sliding contact with at least a portion of the outer seal during movement to the first configuration.
7. The fuel cell stack assembly of claim 1, further comprising a controller configured to act as a membrane between the first configuration and the second configuration, as part of a fuel cell startup and / or shutdown procedure.
2. The fuel cell stack of claim 1, wherein the membrane is movable in an intermediate configuration in which a portion of the air flow conduits of each of the cells of the fuel cell stack is obscured, and the other air flow conduits of each of the cells of the fuel cell stack are non- Fuel cell stack assembly.
2. The fuel cell stack of claim 1, wherein the membrane is configured such that the air flow conduit of the first selected cell in the fuel cell stack is obscured and the air flow conduit of the second selected cell in the fuel cell stack is movable in a non- Battery stacking assembly.
13. The fuel cell stack assembly of claim 12, further comprising a controller configured to operate the membrane between the membrane configurations according to the hydration level and / or the cell voltage level of the fuel cell.
A method of operating a fuel cell stack assembly,
Mounting a movable membrane on a stack of fuel cells, each fuel cell having an air flow conduit having a feed / vent vent located on the vent face of the stack, Mounting the movable membrane to form an array over the ventilating surface of the sieve;
And driving the membrane between a first configuration in which the vent surface is obscured and a second configuration in which the vent surface is not obscured.

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